Description: (Applicant's Description) With the support of the NCDDG, Geron has established over the last five years an efficient program for the screening/identification and characterization of telomerase inhibitors. Our challenge is now to move those discovery assets to human clinical study. The role of medicinal chemistry in this process is a supportive one. Our first responsibility is to refine existing lead candidates through a thorough understanding of the structure-activity and structure-liability correlations. The first and consuming priority is to accomplish this with Lead Series A {derived by the rational approach) and with Lead Series B {from screening of high diversity combinatorial libraries). But implicit in this effort, is the duty to identify potential backup series. If the structure-liability correlation proceeds to the point of making further work in the series untenable, biological colleagues need to have the medicinal chemistry group immediately be able to identify a promising backup series for biological continuity.